This invention relates to the construction of a pallet of the general type which have come to be known an expendable pallets.
Expendable pallets generally comprise a deck or platform having some degree of rigidity supported in spaced relation from the floor by a plurality of spaced feet. The platform is most commonly a single sheet or superposed sheets of corrugated paperboard, but solid fiberboard, plywood or other sheet material may also be used. The individual feet are generally made of molded plastic such as polystyrene, polyethylene or polypropylene, providing a relatively rigid structure having some elasticity.
The assignee of this invention is the owner of U.S. Pat. No. 3,610,172 for a Pallet Construction of the general type here involved. In the patented structure, the individual feet supporting the deck or platform comprise a frustoconically-shaped cup-like member and a locking ring member. The cup-like member of the patented structure has an upwardly opening mouth with a radially outward extending circumferential flange at the upper periphery thereof. Interiorly and spaced beneath the flange, the cup-like member is provided with a circumferentially extending, inwardly projecting lip or shoulder. The locking ring member of the patented structure is engageable within the cup-like member and is provided exteriorly and generally adjacent to its lower extremity with a circumferentially extending, outwardly projecting locking rib to generally interlock beneath the lip or shoulder of the cup-like member to secure the members together. At its upper periphery the locking ring is provided with a radially outward extending circumferential flange which, in the assembly of the leg, generally overlies the flange on the cup-like member. In the assemblage of the feet to the platform, each foot is installed at a suitable die-cut opening in the platform with the locking ring member disposed above and making engagement with a cup-like member disposed beneath the platform. In the assembly, the platform is secured between the superposed flanges of the members to secure the foot to the platform and to space the platform from the floor.
In the structure of U.S. Pat. No. 3,610,172, the cup-like members occasionally became separated from the locking ring members in the pallet assembly. While the reason for any such separation is difficult to pinpoint, it is possible that only a "false" jam lock between the members was attained rather than an intended interlock. Since the area of engagement between the members is totally obscured in the patented structure, visual confirmation relative to a proper interlock between the members is at best difficult. Also, and particularly if a pallet is heavily loaded, plastic creep conceivably could give rise to a separation between the members in the patented structure. The load on the pallet acts through the locking ring member to effect a radial expansion of the molded plastic cup-like member while the ring member itself may be caused to contract radially. Should the expansion of the cup-like member and/or the contraction of the locking ring member exceed the radial bounds of the locking rib on the locking ring member, the cuplike member will be free to fall away when the load on the cuplike member is suddently relieved, as when the loaded pallet is lifted by fork-lift or other means (because the molded plastic is slow to rebound from the radial deformation). Further, if the load on the pallet acts to deflect the platform downward locally with respect to a foot, such deflection will in turn deflect the flange on the corresponding cup-like member downwardly and tend to pry the cup-like member and locking ring member apart. It is generally an object of this invention to avoid the aforementioned problems and provide a pallet construction wherein the feet elements are far less likely to separate and render the pallet defective or unusable.